The problem is the people who say the Democrats should be more "interventionist" or "strong on defense" are people who think Vietnam was great and the left was wrong for trying to stop the war there.
That's a rather broad claim you're making there. Someone who says that the Dems should be more interventionist might be, for example, saying that the US should stop governments that are commiting genocide against their own citizens from doing so and they may yet still think Iraq and Vietnam were bad ideas.